Getting feet wet with hashes

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

After breaking up a file line by line into array elements. We'll just call the array values $test_name and $test_number for now. Can I created a hash list by taking each element for each line:

%hash1 = ($key=>i++;$test_name=>$element_one,$test_num=>$element_two) 
/*element_one and two are variable names that contain string and numbe
+r respectively */
[download]

and then print them by print"%hash1($test_name) \n";

Edit Masem 2001-10-12 - Code Tags and formatting

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Re: Getting feet wet with hashes by dragonchild (Archbishop) on Oct 11, 2001 at 21:58 UTC
You could ... I don't suggest you do so. The idea behind a hash is to use named keys. What you really want to do is create a list of hashes, using hash references. Better would be to do something like: `while (my $line = <INFILE>) { my @line = split /\t/, $line; my %hash = ( key0 => $line[0], key1 => $line[1], key2 => $line[2], key3 => $line[3], key4 => $line[4], ); print "Key 3 is $hash{key3}\n"; push @lines_of_file, \%hash; }` [download] However, even better would be to use a hashslice, similar to an arrayslice. That syntax would look something like: `while (my $line = <INFILE>) { my %hash; @hash{qw(key0 key1 key2 key3 key4)} = split /\t/, $line; print "Key 3 is $hash{key3}\n"; push @lines_of_file, \%hash; }` [download] The two snippets produce identical results, except the second is, in my mind, easier to handle. Some prefer the first, and that's perfectly fine. ------ We are the carpenters and bricklayers of the Information Age. Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.	[reply] [d/l] [select]
Re: Getting feet wet with hashes by arturo (Vicar) on Oct 11, 2001 at 21:55 UTC
Your syntax is incorrect, but you have the basic idea. `%hash` refers to the hash, `$hash{$key}` refers to the value contained in `%hash` that's associated to `$key` (the value is a scalar, so think of $ as referring to scalars and you'll have it. I don't know whether `$key=>i++`, does what you want it to (even with the correction) but assuming `i` is a variable, you need to add the `$` to the front of it. Note also that hash keys occur inside curly braces `{}`. Final note: perl doesn't support C-style comments -- # marks the rest of a line as a comment. hth! `perl -e 'print "How sweet does a rose smell? "; chomp ($n = <STDIN>); +$rose = "smells sweet to degree $n"; other_name = rose; print "$oth +er_name\n"'` [download]	[reply] [d/l] [select]